1. Field of the Invention
The present invention relates to connectors and connector combination which may be suited for balanced transmission.
2. Description of the Related Art
When transmitting data among computers, peripheral equipments, circuit boards, and the like, either the unbalanced transmission or the balanced transmission may be employed. The unbalanced transmission transmits the data by a signal voltage with respect to a ground potential. On the other hand, the balanced transmission transmits the data by differential signals using a potential difference between a signal pair. The balanced transmission is employed in various fields because the balanced transmission is less affected by noise compared to the unbalanced transmission.
A connector combination of a plug connector and a jack connector, may be used for the balanced transmission. A conventional plug connector may include a ground contact formed by a plate-shaped conductor, and a signal contact pair connecting to a signal line pair, which are alternately arranged in a longitudinal direction of the plug connector. On the other hand, a conventional jack connector may have a corresponding structure to receive the plug connector. But when the ground contacts and the signal contact pairs are alternately arranged, the number of parts forming the connector combination becomes relatively large. In addition, it may be difficult to reduce the pitch at which the ground contacts and the signal contact pairs are alternately arranged. In other words, it may be difficult to provide a large number of signal contact pairs without increasing the size of the plug connector along the longitudinal direction thereof.
In the general plug connector for the balanced transmission, the signal contacts forming the signal contact pair are arranged in a direction perpendicular to the longitudinal direction thereof. On the other hand, a plug connector (hereinafter referred to as the “proposed plug connector”) in which the signal contacts forming the signal contact pair are arranged in the longitudinal direction thereof has been proposed in an International Patent Publication WO2003/065512A1, for example. According to this proposed plug connector, a plate-shaped first member having slits extends in the longitudinal direction thereof, and a plurality of second members are fitted into the slits to extend perpendicularly to the longitudinal direction. The first and second members form a ground contact. A plurality of signal contact pairs are arranged along the first member, so that mutually adjacent signal contact pairs are located side by side along the longitudinal direction and each signal contact pair is isolated by the second member. A lead part to connect the ground contact to a circuit board may extend from both ends of the second member.
However, in the general plug connector or the proposed plug connector for the balanced transmission, the ground contact is formed by a plurality of parts, and for this reason, it may be difficult to reduce the number of parts forming the plug connector. In addition, because each signal contact pair of the proposed plug connector is isolated by the second member of the ground contact, it may be difficult to reduce pitch at which the ground contact and the signal contact pairs are alternately arranged.
Furthermore, the proposed plug connector may not be able to cope with the recent demands to perform high-speed signal transmission. One of the functions of the ground contact is to shield each signal contact pair in order to reduce noise. However, if the electromagnetic coupling between the signal contact and the ground contact is relatively strong, a current flowing through the ground contact may resonate. Such a resonance may cause the noise to increase. Because the resonance occurs when a signal transmission frequency reaches a resonance frequency, the signal transmission may not be made at the resonant frequency or higher in the case of a connector in which the electromagnetic coupling is strong between the signal contact and the ground contact. The electromagnetic coupling becomes stronger as the signal and the ground contact become closer to each other in the connector.